The primary aim is to examine, comprehensively and quantitatively, the effects of prenatal exposure to alcohol on the anatomy and physiology of the hippocampal mossy-fiber system. Whether previously described structural alterations in the mossy-fiber system are associated with electrophysiological changes will be determined as well as the functional dependence of these changes on the amount and duration of the alcohol exposure. Thus, prenatal exposure to alcohol will be used as a probe for a better understanding of the functioning of the hippocampus as well as for a further delineation of the factors responsible for the fetal alcohol syndrome. The extent and distribution of abnormal mossy fibers will be studied as a function of the time and dose of alcohol exposure in utero. This will be accomplished by quantitative computer analysis of histological sections stained by the Timm's sulfide silver histochemical technique. Intra- and extracellular recording techniques will be used in the in vitro hippocampal-slice preparation to determine whether ethanol-induced anatomical alterations of the mossy-fiber system are associated with changes in the synaptic and membrane properties of CA3 pyramidal neurons.